Developing device

ABSTRACT

An interlocking mechanism for use in a developing device actuates a mechanism for regulating the condition of the developer on a developing roll correlatively with the movement of a developing unit from a developer supply location to a developer non-supply position and regulates to lower the height of the developer at the position where the developing roll faces the outside of the developing unit. 
     The interlocking mechanism also stops the action of a structure which regulates the condition of developer correlatively with the movement of the developing unit from the developer non-supply position to the developer supply location.

BACKGROUND OF THE INVENTION

1. Technical Field of the Invention

The present invention relates to developing devices for use in suchimage forming apparatus as various kinds of copying machines and laserprinters for forming monocolor images or colored images by selectivelyusing desired colors, and more particularly to a developing deviceprovided with a plurality of developing units accommodating differentcolored toners.

2. Brief Description of Related Art

Generally, a color copying machine for forming colored image is designedto form a colored image by using four colored developers, and developingunits accommodating each colored developer are disposed in a developingdevice in one of the following three methods.

(1) Stationary Method: Each developing unit is disposed at apredetermined position around a photoconductor for selective use.

(2) Rotary Method: Each developing unit is disposed on a rotary supportmember and a desired developing unit is positioned at a developinglocation opposite to a photoconductor by rotating the rotary supportmember.

(3) Reciprocative Movement Method: Each developing unit is disposed on areciprocative movement support member, and a desired developing unit ispositioned at a developing location opposite to a photoconductor byreciprocatively moving the reciprocative movement support member.

The stationary method has problems that the diameter of thephotoconductor becomes large and that there occurs attenuation variationof electrostatic latent images with the passage of time because of thedifference in distance between the position where each electrostaticlatent image is formed and the developing location of each color, and ithas to be rectified.

The rotary method is able to solve the above-mentioned problems inherentin the stationary method, however, there is a problem that toner supplycan not be performed efficiently since developer tends to easily fallout of a developing unit when a rotary support member is rotated withdeveloping units mounted thereon and toner is supplied only to adeveloping unit which is positioned at a predetermined rotativeposition.

The reciprocative movement method has the disadvantageous point that ithas to provide a little larger space in the direction of reciprocatingmovement compared with the rotary method. However, it is provided withcharacteristics which can solve the problems inherent in the rotarymethod. Especially it is arranged for stirring and supplying toners toeach developing unit even when developing operation is not beingperformed. It is, therefore, very advantageous for use in formingcolored images where more toners are consumed than the case whenmonocolor images are formed.

Incidentally, in the developing device of the reciprocative movementmethod, the developing units which are not performing developing processare separated from the photoconductor unlike the stationary method. Itis, therefore, principally not necessary for the developing unit tolower the height of developer accommodated therein at the location ofdevelopment.

However, it may happen to compact and harden the developer when thedeveloping unit is moved from an undeveloping position to the developinglocation again. Once the developer is hardened, it causes to clog aheight regulating plate resulting in the void on an image. Such blockingphenomenon is apt to occur easily since the developer toner is finelyprepared for more improved accuracy for developing process.

Even the developing units at the position outside the developinglocation, when the developer accommodated therein has its heightsufficient for the development at the position facing outside of adeveloping roll, developer may happen to fall out of the developing unitwhen it is moved and stopped or by shock and vibration caused by someother reason. The developer fallen out of the developing unit sticks tothe leading end portion of the unit opposite to a photoconductor andstains the inside of a copying machine. The developer adhered to thefront end portion of the developing unit is attracted by the electricpotential on the side of the photoconductor apart from the supply ofdeveloper from a developing roll when the developing unit is moved tothe location of development and faced the photoconductor, and sticks tothe photoconductor thereby staining an image.

Japanese Published Patent Applications TOKKAI SHO 61-208063 and TOKKAISHO 55-115063 disclose developing devices capable of solving theproblems. The former is designed to lower the height of developer on adeveloping roll at the portion adjacent to the photoconductor especiallywhen the developing unit is positioned at the developing locationopposite to the photoconductor by changing the positions of magnetsarranged in the developing roll at the times of development andundevelopment, while the latter is provided with a shutter blade whichis actuated for scraping off the developer on the developing roll whenthe developing unit is not positioned at the developing location.

These developing devices are arranged to switch the positions ofmagenets and shutter blade corresponding to the position of thedeveloping unit by controlling a driving mechanism specially provided.However, it invites a rise in manufacturing cost since the specialdriving and control mechanisms have to be provided on each one of thedeveloping units. Especially for the color image forming apparatus,considerable rise in manufacturing cost is inevitable since it isprovided with many developing units.

SUMMARY OF THE INVENTION

The main object of the present invention is to provide a developingdevice which is capable of solving the conventional problems by properlyregulating the condition of developer around a developing roll at thetime when development is performed and at the time when development isnot performed without necessitating special driving mechanism andcontrol.

Another object of the present invention is to provide a developingdevice which is capable of properly regulating the condition ofdeveloper around a developing roll simply and accurately by mechanicallyinterlocking with positional switching action of each developing unitwhen it is at the location of operation of the developing positionopposite to a photoconductor and when it is not at the location ofoperation of the developing position.

A further object of the present invention is to provide a developingdevice which is capable of properly regulating the condition ofdeveloper around a developing roll simply and accurately by mechanicallyinterlocking with positional switching action of each developing unitwhen it is at the location of development opposite to a photoconductorand when it is not at the developing location.

Still another object of the present invention is to provide a developingdevice which is capable of accomplishing each one of the above-mentionedobjects by adopting a shutter method and a rotative method of adeveloping roll known well for properly regulating the state ofdeveloper around a developing roll.

These and other objects and features of the present invention willbecome more apparent from the following description taken in conjunctionwith the accompanying drawings which illustrate specific embodiments ofthe invention.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic whole structural view showing a first embodimentof the present invention which is applied to a color copying machine.

FIG. 2 is an enlarged perspective view illustrating a developing deviceof a color copying machine.

FIG. 3 is a perspective view showing a guide means which moves adeveloping unit which has reached a developing location to a location ofoperation.

FIG. 4 is an expanded sectional view showing a state when a developingunit is not at a location of operation of a developing position.

FIG. 5 is an expanded sectional view showing a state when a developingunit is at a location of operation of a developing position.

FIG. 6 is a side view of the upper half portion of a developing deviceillustrating a second embodiment of the present invention.

FIG. 7 is a transverse sectional plan view showing a state when adeveloping unit is at a location of operation of a developing position.

FIG. 8 is a transverse plan view showing a state when a developing unitis not at a location of operation of a developing position.

FIG. 9 is an expanded sectional view showing a state when a developingunit is at a location of operation of a developing position.

FIG. 10 is an expanded sectional view showing a state when a developingunit is not at a location of operation of a developing position.

It is to be noted that like members and units used in each embodimentare designated by like numerals and symbols, and repeated descriptionare omitted.

DESCRIPTION OF THE PREFERRED EMBODIMENT

Embodiments of the present invention will now be described below withreference to accompanying drawings.

FIG. 1 shows the whole structure of a color copying machine to which afirst embodiment of the present invention is applied. An original placedon an original glass table 1 is read as color signals of three primarycolors by a CCD line sensor 2. Each color signal is converted into foursignals of Y (yellow), M (magenta), C (cyan) and B (black) by an imageprocessing circuit and its output signal is transmitted to a laseroptical system 3.

From a laser light generating device 4 in the laser optical system 3,laser light for forming images of each color corresponding to thesignals of Y,M,C and B is irradiated. The laser light is then directedthrough a reflector 5 to a photoconductor 6 which rotates in thedirection of the arrow, and image exposure is performed.

On the surface of the photoconductor 6, a latent image is formed by theimage exposure. For the latent image formed corresponding to the signalY, yellow toner Y is supplied from Y developing unit 7y and an yellowtoner image is formed on the photoconductor 6. In the same manner, eachcolored toner is supplied from M developing unit 7m, C developing unit7c, and B developing unit 7b thereby forming magenta toner image, cyantoner image and black toner image respectively for the latent imagesformed corresponding to the signal M, signal C and signal B.

A sheet of copy paper fed from a paper cassette 9 and transported bytransport rollers 10,11 is wrapped around a transfer drum 8. Onto thepaper wrapped around the transfer drum 8, each colored toner image onthe photoconductor 6 is successively transferred by rotation of thetransfer drum 8 with required number of rotations. The toner images ofeach color being transferred are composed on the copy paper and acolored toner image is formed thereon. The copy paper on which a coloredtoner image is formed is separated from the transfer drum 8 and is thentransported through a transfer belt 12 to a fixing roller 13 where thecolored toner image is fixed and then discharged to a discharge tray 14.

Each color developing unit, 7y, 7m, 7c and 7b (hereinafter called asdeveloping unit 7 when each developing unit is generically called) isvertically supported by an elevation support member 15 in four stages.As shown in FIG. 2, the elevation support member 15 is provided with twosheets of sideboard 16 and four sheets of developing unit support board17. On each one of the developing unit support boards 17, eachdeveloping unit 7y, 7m,7c and 7b is placed, and they are movablysupported and guided back and forth.

The elevation support member 15 is provided with rails 18 mounted on thesideboards 16 and fitted into rails 20 mounted on a pair of stationaryboards 19 fixed on the main body of the machine. The elevation supportmember 15 is vertically movably supported and guided in a fittingrelation between the rails 18,20.

A balancer 21 is mounted on the stationary board 19, and the tip portionof a spring sheet 22 of the balancer 21 is attached to the elevationsupport member 15 so as to always maintain a balanced state irrespectiveof any vertical position of the elevation support member 15.

A driving shaft 23 is hung at the lower portion of the stationary boards19, and a gear 24 fixed to one end of the shaft is engaged with adriving gear 26 of a DC motor 25. Adjacent to both ends of the drivingshaft 23, driving sprockets 27 are fixed, and chains 29 are wound aroundbetween sub-sprockets 28 held on the upper portion of the stationaryboards 19. The chain 29 and the elevation support member 15 areconnected with couplers 30. The elevation support member 15 is thusmoved to a predetermined height of position by driving the chain 29 withthe DC motor 25. Accordingly, a desired developing unit 7 can bepositioned to face the photoconductor 6.

Each developing unit 7 placed on the developing unit support board 17 isbiased backward by a spring 31 and is stopped at a predeterminedretreated position by an unillustrated stopper. At the back end portionof the developing unit 7, a flat spring 32 which is bended in < shape isfixed.

FIG. 1 shows a state when the uppermost developing unit 7y is positionedopposite to the photoconductor 6, where a developing unit positionswitching means 33 is provided at the back of the developing unit 7y foradvancing the developing unit 7 to the developer supply positionopposite to the photoconductor 6.

The developing unit position switching means 33 is provided with, asshown in FIGS. 1 and 3, a stationary frame 34 fixed to the main body ofthe machine, a moving cam 35 movably supported and guided back and forthby guiding long grooves 37,38 with guide pins 39,40, and an eccentricdriver 36 for moving the moving cam 35 back and forth.

The front of the moving cam 35 is formed by a vertical plane 42 at theupper portion and an inclined plane 43 at the lower portion. The movingcam 35 is provided with hollow portion 45 where the eccentric driver 36is positioned, and the front wall of the hollow portion 45 is pressed tocontact the eccentric driver 36 by a spring 44 to move the moving cam 35back and forth by rotation of the driver 36. The eccentric driver 36 isfixed to a cam driving shaft 46, and the cam driving shaft 46 isrotatively controlled by unillustrated motor and clutch.

In order to accurately position the developing unit 7 advanced to adeveloper supply position at the developer supply location, positionregulating members 47 provided with V shape positioning grooves aredisposed on both sides of the photoconductor 6, and positioning rollers48 are fixed on both sides of the developing unit 7 as shown in FIGS. 1and 2. Accordingly, when the developing unit 7 is advanced by theeccentric driver 36 through the moving cam 35, the developing unit 7 isaccurately positioned at the developer supply position by thepositioning rollers 48 and the position regulating member 47 (refer toFIG. 5 ). When the eccentric driver 36 is retreated, the developing unit7 is also retreated and engagement with the position regulating memberis released thereby causing the developing unit to move freely upwardlyand downwardly (refer to FIG. 4).

As illustrated in FIGS. 4 and 5, each developing unit 7 suppliesdeveloper to a developing roll 52 from bucket sections 50a, 50b providedwith stirring means 51a, 51b. The developing roll 52 transports thedeveloper by magnets stored therein (magnetic pole is only shown) in thedirection of the arrow (FIG. 5) under a state that magnet is absorbed.Accordingly, the developer is transported to the developing sectionopposite to the photoconductor 6, wherein the height of the developerpassing through is regulated by a height regulating plate 53. Thedeveloper used for developing process is removed at non-magnetic portion55 of the developing roll 52 and is returned to the bucket section 50aagain. The developer is then mixed and stirred with new toner andthereafter is supplied to the developing roll 52. The stirring means51a, 51b and the developing roll 52 are always rotatively driven by anunillustrated motor.

In FIGS. 4 and 5, the numeral 70 designates a shutter which is arrangedto obstruct or limit the movement of developer from the bucket section50a of the developing unit 7 to the developing roll 52. The shutter 70is pivotally supported by a shaft 71 at its central portion, and thelower end portion 70a is movably arranged toward and away from thedeveloping roll 52. The upper end portion 70b of the shutter 70 isfastened to one end of a tension spring 72 and the shutter is biased tothe clockwise direction.

A ceiling plate 73 is fixed to the elevation support member 15 so as topositioned above each developing unit 7 (the developing unit supportplate 17 may also be used as the ceiling plate).

A stopper portion 74 is downwardly and protrusively provided on theceiling plate 73 for regulating the pivotal movement of the shutter 70at a predetermined position by the tension spring 72. The other end ofthe tension spring 72 is fastened to a front end bent portion 75 of theceiling plate 73.

A shutter position switch means 77 comprised of the tension spring 72and the stopper portion 74 switches over the shutter 70 to the operatingposition as shown in FIG. 4 when the developing unit 7 moves from thedeloper supply location to a retreated position. At this stage, theupper end portion 70b contacts and is parallel with the stopper portion74, and the lower portion 70a contacts the developing roll 52.Accordingly, the developer supplied and transported from the bucketsection 50a to the developing roll 52 is scraped off by the shutter 70and is not transported to the developing section 54.

On the other hand, when the developing unit 7 is moved from theretreated position to the developer supply location, the shutterposition switch means 77 switches over the shutter 70 to thenon-operating position as shown in FIG. 5. In other words, when thedeveloping unit 7 is advanced, the upper end portion 70b of the shutter70 is obstructed by the stopper portion 74 thereby pivotally moving theshutter 70 counterclockwise, while the lower end portion 70a of theshutter 70 loses contact with the developing roll 52. Accordingly, thedeveloper supplied from the bucket section 50a to the developing roll 52is transported to the developing section 54.

Now, a function of the device will be described. The elevation supportmember 15 is raised from the lowermost position to have a desired colordeveloping unit 7 positioned opposite to the photoconductor 6, and thenthe developing unit 7 is moved forward to be positioned at the developersupply position with the developing unit switch means 33. Then, theshutter 70 is switched over to the non-operating position as shown inFIG. 5, and the developer stirred in the bucket sections 50a, 50b issupplied to the developing roll 52 without having any obstruction by theshutter 70. Thereafter, the developer is transported to the developingsection 54 after being regulated by the height regulating plate 53. Alatent image on the photoconductor 6 is thus visualized by toner. Thevisualized toner image is transferred onto a copy paper on the transferdrum 8. The developer used for the developing process is removed fromthe developing roll 52 at the non-magnetic section 55 to return to thebucket section 50a.

When the developing process is finished by the developing unit 7, thedeveloping unit 7 is released from the pressure of the developing unitposition switch means 33 and is moved backward by a spring 31. Then, theshutter 70 is switched over to the operating position as shown in FIG.4, and the movement of the developer to the developing roll 52 isstopped thereby causing the height of the developer on the developingroll 52 to be covered.

In the meantime, the stirring of the developer is always carried out bycontinual rotation of the stirring means 51a, 51b and the developingroll 52. Sufficient stirring is thus ensured, and toner density of thedeveloper in the developing unit 7 is advantageously maintainedconstant.

In the same manner as above-mentioned, when the next developing unit 7is moved backward after developing process, the developer on thedeveloping roll 52 runs out or the height of the developer is lowered.Thus, even if the developing unit 7 is positioned opposite to thephotoconductor 6 and moved forward to the developer supply location,there is no problem of compacting and hardening the developer since thedeveloper is run out or the height of the developer is lowered on thedeveloping roll 52. Accordingly, there is no problem of occurrence of avoid on an image.

Moreover, fall out of the developer caused by shock and vibration isprevented at the time when the elevation support member 15 and thedeveloping unit 7 start or stop their action. Accordingly, the problemof staining the leading end portion of the developing unit 7 and theinside of the copying machine can be solved, and further when thedeveloping unit 7 is positioned at the developing and the operatinglocation, the toner sticked to the front end portion of the developingunit 7 is attracted by electric potential of the photoconductor 6 thusavoiding stains on an image.

FIGS. 6 through 10 illustrate a second embodiment of the presentinvention which is applied to almost the same type of a copying machineas shown in FIG. 1 of the first embodiment of the present invention.Each developing unit 7 is also basically the same as the ones in thefirst embodiment of the present invention.

Stirring means 51a, 51b and developing roll 52 are driven from the sideof the main body of the machine. As shown in FIG. 7, a developing rollgear 58 is mounted on a driving shaft 56 extended from one end of adeveloping roll 52 through a one way clutch 57, and is engaged with adriving gear 59 of the main body of the machine under a state that thedeveloping unit 7 is positioned at a developer supply location. Bucketgears 61 are also fixed to one end portion of driving shafts 60 of thestirring means 51a, 51b respectively, and the developing roll gear 58and the bucket gear 61 are interlocked through an idle gear 62 so as torotate in the same direction.

A transmission gear 71 is provided on a shaft 63 extended from anotherend portion of the developing roll 52 through one way clutch 70, and anidle gear 72 which engages with the transmission gear is also provided.There is also disposed a rack 73 in the vertical direction which engageswith the idle gear 72 under the state that the developing unit 7 ispositioned at a retreated position, and is fixed to the main body of themachine.

In FIGS. 7 and 8, a simplified position switching means 33 is shownwhich is arranged to advance the developing unit 7 by directly pressingthe unit 7 with an eccentric cam 68 fixed to a drive operating shaft 67.

Now, a function of the device will be described. The elevation supportmember 15 is first raised from the lowermost position to have a desiredcolor developing unit 7 positioned opposite to the photoconductor 6, andthe developing unit 7 is moved forward to be positioned at a developersupply location by the position switching means 33. Then, as shown inFIG. 7, the developing roll gear 58 is engaged with the driving gear 59to rotate the developing roll 52 and the stirring means 51a, 51b in thebucket sections 50a, 50b.

As a result, the developer is stirred and circulated in the bucketsections 50a, 50b and supplied to the developing roIl 52 as shown inFIG. 9 where the height of the developer is regulated by a heightregulating plate 53 and the developer is fed to a developing section 54.A latent image on the photoconductor 6 is thus visualized by toner, andthe visualized toner image is transferred onto a copy paper on atransfer drum 8. The developer after developing process is removed at anon-magnetic section 55 of the developing roll 52 and is returned to thebucket section 50a.

When the developing process is finished by the developing unit 7, thedeveloping unit 7 is released from the pressure of the position switchmeans 33 and is moved backward by a spring 31. Then, as shown by thesolid line in FIG. 7, the engagement of the driving gear 59 with thedeveloping roll gear 58 is released and the developing roll 52 and thestirring means 51a, 51b are stopped.

On the other hand, the idle gear 72 is engaged with a rack 73 by thebackward movement of the developing unit 7 as shown in FIGS. 6 and 8.Under the state, when an elevation support member 15 is moved, forinstance, upwardly in order to have a developing unit 7 positionedopposite to the photoconductor 6, the transmission gear 71 startsrotation through the idle gear 72, and the developing roll 52 startsrotation through a one way clutch 70. At this stage, the driving shaft56 also starts rotation, however, rotative force is not transmitted tothe developing roll gear 58 since a one way clutch 57 is providedthereat and the stirring means 51a, 51b are thus not rotated. As aresult, the developing roll 52 is rotated in the direction of the arrowas shown in FIG. 10 under a state that developer is not supplied fromthe bucket section 50a, and the developer held on the developing roll 52with ordinary height is removed by passing through the non-magneticsection 55 thereby causing the height of the developer to be lowered.

In the same manner as above-mentioned, when the next developing unit 7is moved backward and starts upward movement the height of developer onthe developing roll 52 is lowered. Incidentally, when the elevationsupport member 15 moves downward, the developing roll 52 is notreversely rotated even if the transmission gear 71 is reversely rotatedsince a one way clutch is not provided. Accordingly, even when thedeveloping unit 7 is moved again to the position opposite to thephotoconductor 6 and is advanced to the developer supply location, thedeveloper is held on the developing roll 52 with an ordinary height sothat bad effects can be avoided.

In the above-mentioned embodiment, the developing roll 52 is arranged torotate only when the elevation support member 15 moves upwardly,however, as shown in FIG. 7, the developing roll 52 can be arranged torotate in the same direction even when the elevation support member 15moves downwardly by providing a second transmission gear 65 on the shaft63 through one way clutch 64 with a second rack 66 to which thetransmission gear 65 is engaged when the developing unit 7 movesbackward.

In the case when the height can be lowered without rotating thedeveloping roll 52 many times, the rack 66,73 may be provided at theposition adjacent to and facing the photoconductor 6, and at the otherpositions, it may be arranged to drive the stirring means 51a, 51b.Instead of making use of the non-magnetic section 55 of the developerdetaching function for lowering the height of the developer as describedin the second embodiment of the present invention, a scraper 100 may beprovided as shown by phantom line in FIG. 9. Needless to say the drivingmeans of the developing roll 52 and stirring means 51a, 51b mayoptionally be changed.

Moreover, the present invention may be applied to a moving method suchas rotary method not limiting to the elevation method. Not limiting to acolor copying machine wherein an electrostatic latent image is composedcorresponding to each color as described in the above embodiment, it mayalso be applied to a multicolor copying machine wherein a plurality ofdeveloping units accommodating different colored developers areselectively used for visualizing the electrostatic latent images formedseparately without having color decomposition.

The shutter in the first embodiment of the present invention may beactuated correlatively with the movement of each developing unit betweenthe developing location and non-developing position, and the developingsleeve in the second embodiment of the present invention may be actuatedcorrelatively with the movement of the developing unit on the supportmember.

The present invention may also be applied to the case when a rotarysupport member is used for selectively moving each developing unit tothe developing position. Moreover, in the present invention, any movingmethod may be adopted for movement of each developing unit between aposition adjacent to a photoconductor, i.e. an image support member anda position away from the image support member.

Although the present invention has been fully described by way ofexamples with reference to the accompanying drawings, it is to be notedthat various changes and modifications will be apparent to those skilledin the art. Therefore, unless otherwise such changes and modificationsdepart from the scope of the present invention, they should be construedas being included therein.

What is claimed is:
 1. A developing device for developing an electrostatic latent image on an image support member, comprising:a plurality of developing units having developing rolls which are rotatively driven for supplying different colored developers to the image support member; a position changeover means for switching over positions of each developing unit between a developer supply location adjacent to the image support member and a developer non-supply position away from the image support member; a developer condition regulating means for regulating the condition of developer on the developing roll to lower the height of the developer at least at the portion where the developing roll faces the outside of the developing unit; and an interlocking means for actuating or stopping the action of the developer regulating means correlatively with the movement of each developing unit between the developer supply location and the developer non-supply position.
 2. A developing device as claimed in claim 1, wherein the position changeover means comprises:a movable support member supporting each developing unit and being movable in a predetermined direction for selectively switching over the position of one of the developing units to the developing location opposite to the image support member, and a mechanism of forward and backward movement of a developing unit for advancing on the movable support member a developing unit at the developing location to the developer supply location adjacent to the image support member and for moving backward the unit from the location.
 3. A developing device as claimed in claim 2, wherein the interlocking means actuates or stops the action of the developer condition regulating means correlatively with the movement of the movable support member.
 4. A developing device as claimed in claim 2, wherein the interlocking means actuates or stops the action of the developer condition regulating means correlatively with the forward and backward movement of a developing unit on the movable support member.
 5. A developing device for developing an electrostatic latent image on an image support member, comprising:a plurality of developing units for supplying different colored developers to the image support member, each developing unit having a rotatively driven developing roll and a developer stirring means for stirring and supplying developer to the image support member; a developing unit support member for movably supporting each developing unit between a developer supply location adjacent to the image support member and a developer non-supply position away from the image support member; a position changeover means for moving each developing unit between the developer supply location and the developer non-supply position; a shutter for regulating supply of developer to the developing roll; and an interlocking means for switching over the shutter positions where supply of developer is carried out or regulated correlatively with the movement of each developing unit between the developer supply location and the developer non-supply position.
 6. A developing device as claimed in claim 5, wherein the shutter is moved to approach or contact the circumferential surface of the developing roll at the position where supply of developer is regulated.
 7. A developing device as claimed in claim 5, wherein the position changeover means comprises:a support member moving mechanism for moving the developing unit support member in a predetermined direction and for selectively moving one of the developing units to the developing location opposite to the image support member; and a mechanism of forward and backward movement of a developing unit for advancing on the developing unit support member a developing unit at the developing location to the developer supply location adjacent to the image support member and for moving backward the unit from the location.
 8. A developing unit as claimed in claim 7, wherein the developing unit support member moving mechanism causes the support member to reciprocate in the vertical direction.
 9. A developing device as claimed in claim 7, wherein the interlocking means switches over the shutter to regulating or non-regulating position correlatively with the forward and backward movement of a developing unit on the support member.
 10. A developing device as claimed in claim 9, wherein the interlocking means comprises:an energizing member for energizing the shutter at either one of regulating or non-regulating positions, and a stopper for regulating the movement of the shutter corresponding to the forward or backward position of a developing unit on the support member.
 11. A developing device as claimed in claim 10, wherein the shutter is pivotally supported by a developing unit and is switched over to the regulating or non-regulating position with the shutter being energized by the energizing member to the side of the regulating position, and the stopper being provided on the support member for stopping the shutter at the position corresponding to the forward and back movement of a developing unit.
 12. A developing device for developing an electrostatic latent image on an image support member, comprising:a plurality of developing units for supplying different colored developers to the image support member, each developing unit have a rotatively driven developing roll and a developer stirring means for stirring and supplying developer to the image support member; a position changeover means for switching over positions of each developing unit between a developer supply location adjacent to the image support member and a developer non-supply position away from the image support member; a developer detaching means for detaching the developer supplied onto the surface of a developing roll; a first interlocking means for connecting or disconnecting both the developing roll and the stirring means with a driving means correlatively with the movement of a developing unit between a developer supply location and a developer non-supply position; and a second interlocking means for rotating the developing roll correlatively with the movement of a developing unit to the developer non-supply position, the rotation being carried out until the developer detached portion reaches at least at the position where the developing roll faces the outside of the developing unit.
 13. A developing device as claimed in claim 12, wherein the developer detaching means is a non-magnetic portion arranged in a magnet member provided in the developing roll where developer is magnetically held on the developing roll.
 14. A developing device as claimed in claim 12, wherein the position changeover means comprises:a movable support member supporting each developing unit and being moved in a predetermined direction for selectively switching over the position of each developing unit to the developing location opposite to the image support member; and a mechanism of forward and backward movement of a developing unit for advancing on the movable support member a developing unit at the developing location to the developer supply location adjacent to the image support member and for moving backward the unit from the location.
 15. A developing device as claimed in claim 14, wherein the first interlocking means performs engagement or disengagement correlatively with the forward and backward movement of a developing unit on the support member.
 16. A developing device as claimed in claim 15, wherein the first interlocking means is provided with a developing gear connected to a developing roll through a one way clutch and also to the developer detaching means without a clutch, and the gear is engaged or disengaged with a driving gear positioned at a predetermined location correlatively with the movement of a developing unit.
 17. A developing device as claimed in claim 14, wherein the second interlocking means is caused to be operable or inoperable correlatively with the forward and backward movement of a developing unit on the support member and is actuated correlatively with the movement of a developing unit from the developing location to the non-developing position.
 18. A developing device as claimed in claim 17, wherein the second interlocking means comprises:a rack provided at a predetermined position along the direction of movement of a developing unit by the support member; and a gear connected to a developing sleeve through a one way clutch for engaging and disengaging with the rack correlatively with forward and backward movement of a developing unit on the support member. 